To get my scanner working again, first I installed the OpenSource files from TWAIN SANE. First I installed libusb.pkg, then sane-backends.pkg, and finally sane-preference-pane.pkg.
With the freeware Scan Again for the SANE Extension (Scanner Access Now Easy), I could finally use my Agfa SnapScan 1212u again. After launching the app, it bounces a long time, but it will eventually work. There are not many preferences, but enough to do all important scans I need.

